LT1673 LINER [Linear Technology], LT1673 Datasheet - Page 11

• Manufacturer Part Number: LT1673
• Description: Auto-Polarity, Ultralow Voltage Step-Up Converter
• Manufacturer: LINER [Linear Technology]

OPERATION
on the application and capacitor sizing, since the load on
the V
magnitude higher than 8μA.
VSTORE
The VSTORE output can be used to charge a large storage
capacitor or rechargeable battery. Once V
regulation, the VSTORE output will be allowed to charge
up to the clamped VAUX voltage (5.25V typical). The
storage element on VSTORE can then be used to power
the system in the event that the input source is lost, or
is unable to provide the current demanded by the V
V
If VAUX drops below VSTORE, the LTC3109 will automati-
cally draw current from the storage element. Note that it
may take a long time to charge a large storage capacitor,
depending on the input energy available and the loading
on V
OUT2
OUT
OUT2
and LDO outputs.
and VLDO.
output, when enabled, is likely to be orders of
(Refer to the Block Diagram)
5.0
2.5
3.0
2.0
1.0
5.0
2.5
3.0
2.0
1.0
5.0
2.5
0
0
0
0
0
0
10
Figure 1. Output Voltage Sequencing
(with V
OUT
OUT
20
has reached
VSTORE
PGOOD
Programmed for 3.3V). Time Not to Scale
VLDO
VAUX
V
OUT
30
OUT
TIME (ms)
,
40
Since the maximum charging current available at the
VSTORE output is limited to about 15mA, it can safely be
used to trickle charge NiCd or NiMH batteries for energy
storage when the input voltage is lost.
Note that VSTORE is not intended to supply high pulse
load currents to V
handled by the V
Short-Circuit Protection
All outputs of the LTC3109 are current limited to protect
against short circuits to ground.
Output Voltage Sequencing
A timing diagram showing the typical charging and voltage
sequencing of the outputs is shown in Figure 1. Note that
the horizontal (time) axis is not to scale, and is used for
illustration purposes to show the relative order in which
the output voltages come up.
50
60
OUT
OUT
70
reservoir capacitor.
. Any pulse load on V
3109 F01
80
LTC3109
OUT
must be
11
3109fa